To conduct a drill stem test of a well that has an irregularly enlarged or "washed-out" bore, it is common practice to use packer elements of the type that can be inflated by a downhole pump to isolate and seal off the well interval to be tested. To properly inflate the packer elements it is preferable to provide for the equalization of the pressure of fluids in the space between the packers with the pressure above the upper packer element while inflation fluid under pressure is being supplied to the respective interiors of the packers via an inflation passage that leads from the outlet of the pump. During the test, of course, such pressure equalization must be stopped. At the end of the test the pressures must again be equalized and the packer elements deflated so that the string of tools can be removed from the well or moved to another test elevation therein.
An apparatus for equalizing pressures and for inflating and deflating inflatable packer elements is shown in Conover U.S. Pat. No. 3,439,740 issued Apr. 22, 1969. The apparatus disclosed in this patent, although widely used, is believed to have a number of shortcomings. For example, pressure equalization is accomplished by separate flow paths and valve systems which is an unduly complicated arrangement that can be subject to plugging or other malfunction. Another problem with the Conover apparatus is that in order to deflate the packers at the end of a test, a rather complicated clutch structure that is actuated by setting down weight and rotating the pipe must be operated in order to shift a shuttle valve to a position where a deflate port is opened up to vent the interiors of the packer elements to the well bore.
It is a general object of the present invention to provide a new and improved pressure equalizing and packer deflating valve apparatus useful in straddle testing operations using packer elements that are inflated by a downhole pump that is operated in response to pipe rotation.
Another object of the present invention is to provide a new and improved valve system of the type described that is more compact and simple in construction and operation, and thus more reliable for use in well testing operations.